This invention relates to a method of encapsulating hardware on a chip to allow multi-tasking of microcode. An additional embodiment of the present invention involves a method to reuse a single existing xe2x80x9cToken-Ringxe2x80x9d embedded processor and microcode for multiple ports on a chip.
Before going into the specific embodiments of the present invention, it would be most helpful to review the background on xe2x80x9cTokensxe2x80x9d and xe2x80x9cToken-Ring-Networksxe2x80x9d.
A token is a unique structure data object or message that circulates continuously among nodes of a token ring and describes the current state of the network. Before any node can send a message, the node must first wait to control the token. A token can also be considered as any nonreducible textural element in data that is being parsed-for example, the use in a program of a variable name, a reserved word, or an operator. Storing tokens as short codes shortens program files and speeds execution.
In authentication systems, some type of physical device, such as a card impregnated with a magnetic stripe, a smart card, or a calculator-like device that generates a password, must be in the individual""s possession in order to access a network. The Token itself is not sufficient; the user must also be able to supply something memorized, such as a personal identification number (PIN). Combining xe2x80x9csomething you havexe2x80x99 with xe2x80x9csomething you knowxe2x80x9d, provides strong authentication.
In local area networks (LAN), a network protocol in which a special bit configuration(Token), is circulated among the work stations, is called xe2x80x9cToken Passingxe2x80x9d. A node can send information across the network only if the node can obtain an available token, in which case the node converts the token into a data frame containing a network message. Nodes constantly monitor the network to catch data frames addressed to them. Because token-passing rules out the data collisions that occur when two devices begin transmitting at the same time, this channel access method is preferred for large, high-volume networks.
The term, Token-Ring-Network , refers to a local area (LAN) architecture that combines token-passing with a hybrid star/ring technology developed by IBM Corporation, which employs a Multi-Access Unit at its hub as demonstrated in FIG. 1. This unit is wired with twist-pair cable in a star configuration with up to 255 workstations, but the resulting network is actually a decentralized ring network.
Thus a token ring network is a local area network formed in a ring or closed loop topology that employs token passing as a means of regulating traffic on the line. On a token ring network, a token governing the right to transmit is passed from one station to the next station in a physical circle. If a station has information to transmit, it xe2x80x9cseizesxe2x80x9d the token, marks it as being in use, and inserts the information. The xe2x80x9cbusyxe2x80x9d token, plus message, is then passed around the circle, copied when it arrives at its destination, and eventually returns to the sender. The Sender removes the attached message and then passes the freed token to the next station in line. Token ring networks are defined in the IEEE 802.5 standards.
A token-passing, ring-shaped local area network developed by the IBM Corporation, operates at 4 or 16 megabits per second. With a standard telephone wiring, the token-ring-network uses the star-shaped clusters of up to eight workstations connected to a wiring concentrator, as noted above, which is called a Multistation Access Unit or xe2x80x9cMSAUxe2x80x9d. This in turn is connected to the main ring.
The development of a follow-on Token Ring Switch product has one of its requirements, the need to be far less costly than its predecessor. One classical way to accomplish this is through the integration of multiple ports into a single VLSI chip. The simple replication of an individual port, a multiple number of times and duplicating all circuits, results only in limited or minor cost reduction.
Another approach is to replicate only the minimal amount of chip circuitry for a single port operation, a multiple number of times. Then, integrate a single copy of hardware that can support the major functions common to all ports. One of the largest functions required in a Token Ring chip is the microprocessor and the microcode it executes to support media access control (MAC) layered protocols. MAC, in a computer network, represents the layer that controls under what circumstances a workstation can get access to the physical media in order to originate a message to another workstation.
he problem with sharing or multi-tasking a single microprocessor across multiple ports is that it requires an elaborate and costly effort to adapt, modify, and rewriting of existing microcode. Extensive effort has gone into the development and testing of existing microcode that supports Token Ring. The re-use of the microcode, mostly in an xe2x80x9cas isxe2x80x9d condition is required to increase effectiveness and reduce costs.
The present invention resolves these problems. It further describes a method that easily encapsulates existing hardware and allows the use of existing microcode to be extended to a multi-tasking environment at a substantially reduced cost and with greater efficiency.
Another embodiment of this invention describes a system and method to reuse a single existing Token Ring macro with embedded processor and microcode for multiple ports on a chip.